The lubrication system of an engine pressurizes and distributes lubrication fluid, e.g. oil, to the engine lubrication circuits by use of a pump such as a variable displacement vane pump (VDVP). A variable displacement sliding vane pump may employ a rotor and a slide with multiple radially extending slidable vanes and cavities which can vary the volume of fluid delivered to the lubrication circuits. The slide is eccentrically offset from the rotor to create fluid chambers defined by the vanes, rotor and inner surface of the slide. A compression spring positions the slide to create large fluid chambers as the default.
When the engine requires less volume of fluid or less oil pressure by the pump, a pressure regulator directs fluid from the pump output line to a regulating chamber in the pump. Pressure in the regulating chamber pivots the slide against the force of the spring to more closely align the centers of the rotor and slide, thereby reducing the size of the fluid chambers. This reduces the amount of fluid drawn into the pump from the fluid reservoir and likewise, the amount of fluid output by the pump and thereby reduces the oil pressure as well.
U.S. Pat. No. 6,763,797 discloses a variable displacement pump in which pump outlet pressure is used to bias the position of a slide (also referred to as a cam ring), thereby changing the eccentricity of the slide with respect to the rotor axis and consequently varying the pump displacement. By varying the pump displacement relative to pump outlet pressure, the pump outlet pressure can be controlled based on engine flow requirements. The pressure regulation characteristics of the pump are determined by calibrating a reaction spring that counterbalances the hydraulic forces acting on the slide.
However, further improvements to variable displacement vane pumps and, in particular, variable displacement vane pumps with a pivotable slide for use in engine lubrication systems are desirable. In addition, other improvements, desirable features and characteristics are desirable and will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.